Propene oxidative carbonylation

Solid catalysts for the metathesis reaction are mainly transition metal oxides, carbonyls, or sulfides deposited on high surface area supports (oxides and phosphates). After activation, a wide variety of solid catalysts is effective, for the metathesis of alkenes. Table I (1, 34 38) gives a survey of the more efficient catalysts which have been reported to convert propene into ethene and linear butenes. The most active ones contain rhenium, molybdenum, or tungsten. An outstanding catalyst is rhenium oxide on alumina, which is active under very mild conditions, viz. room temperature and atmospheric pressure, yielding exclusively the primary metathesis products. 

Functionalization of hydrocarbons from petroleum sources is mainly concerned with the introduction of oxygen into the hydrocarbon molecule. In general, two ways are open to achieve oxygen functionalization oxidation and carbonylation. Oxidation is commonly encountered in the synthesis of aromatic acids, acrolein, maleic anhydride, ethene oxide, propene oxide, and acetaldehyde. Hydroformylation (CO/H2) (older literature and the technical literature refer to the oxo reaction) is employed for the large-scale preparation of butanol, 2-ethylhexanol, and detergent alcohols. The main use of 2-ethylhexanol is in phthalate esters which are softeners in PVC. The catalysts applied are based on cobalt and rhodium. (For a general review see ref. 3.)... 

The development of a new high-performance fluoro-elastomer based on perfluoromethyl perfluorovinyl ether has already been mentioned (see ref. 305 and p. 26). Preparation of the ether involves ring-opening of perfluoro-propene oxide with trifluoromethoxide ion generated in situ from carbonyl fluoride. Similarly, perfluorobut-3-enyl perfluorovinyl ether (58) can be synthesized from perfluoropropene oxide and perfluoroglutaryl difluoride > ... 

An important further development came from the group of Yang et al., who reported on a catalytic variant of the carbonylative annulation of benzyl alcohols (Scheme 15.14). The best results were achieved by generating the Pd-complex in situ from the reaction of Pd(OAc)2 with tetramethyl thiourea in the presence of ammonium acetate and propene oxide in tetrahydro-furan. The feasibility of Pd-thiourea as a unique catalyst has been demonstrated in the construction of a fused pyran y-lactones 45 and 46 (Scheme 15.14), the key intermediate in the total syntheses of micrandilactone A" and crisamicin A . 

Cobalt carbonyls are the oldest catalysts for hydroformylation and they have been used in industry for many years. They are used either as unmodified carbonyls, or modified with alkylphosphines (Shell process). For propene hydroformylation, they have been replaced by rhodium (Union Carbide, Mitsubishi, Ruhrchemie-Rhone Poulenc). For higher alkenes, cobalt is still the catalyst of choice. Internal alkenes can be used as the substrate as cobalt has a propensity for causing isomerization under a pressure of CO and high preference for the formation of linear aldehydes. Recently a new process was introduced for the hydroformylation of ethene oxide using a cobalt catalyst modified with a diphosphine. In the following we will focus on relevant complexes that have been identified and recently reported reactions of interest. 

Despite the rich chemistry of 45 [18], the only method for accessing this compound is the oxidation of the corresponding alcohol derived from 2-methyl-2-propen-l-ol or other sources, which can be obtained through multi-step operations. In contrast to the known methods, 45 can be readily derived from 44 and 50 by a simple one-pot operation. Since the propargylic alcohol 50 a is readily accessed from a ketone or aldehyde, realization of the transformation of 50 to 45 through a one-pot procedure provides a novel method for carbonyl olefmation of ketones or aldehydes. 

The carbonyl ylide precursor can be generated by lead tetraacetate oxidation of the hydrazone 58. Thermolysis of 59 in the presence of perdeuterated acetone led to a variety of products, some of which are shown above. An internal quench of the ylide via a 1,4-proton migration led to enol ether 61, while cycloaddition with perdeuterated acetone formed the dioxolane 62 and its regioisomer. Interestingly, the presence of products such as acetone and propene-t/s are proposed to indicate a reversible fragmentation of the ylide to a carbonyl derivative and a carbene. 

Carbonyl-substituted nitrones are formed as mixture of (E)- and (Z)-stereo-isomers. By coordination to a Lewis acid, the (Z)-isomers are expected to be more stabilized due to tight complexation. Thus, a 2.8 1 ( /Z)-mixture of A -(methoxy-carbonylmethylene)methylamine A -oxide isomerizes to the (Z)-isomer in the presence of MgBr2-Et20 and undergoes a regio- and exo-selective cycloaddition reaction to 2-propen-l-ol to give the isoxazolidine-5-methanol as a single product... 

Hickinbottom and co-workere have recently published evident, casting doubt on earlier beliefs that epoxides were intermediates in 11nformation of carbonyl compounds during olefin oxidation by chroma add. For example, 2-methyl-l, 1 diphenyl 1 -propene (Eq. Ill) gave-good yiold of the corresponding epoxide in acetic anhydride along wii-1. 

The most common oxidation states and corresponding electronic configurations of rhodium are +1 (tf8), which is usually square planar although some five coordinate complexes are known, and +3 (T) which is usually octahedral. Dimeric rhodium carboxylates are +2 (oxidation states —1 (industrial applications include rhodium-catalyzed carbonylation of methanol to acetic acid and acetic anhydride, and hydroformylation of propene to tf-butyraldehyde. Enantioselective catalytic reduction has also been demonstrated. 

ACROLEIN AND DERIVATIVES. Acrolein (2-propenal), C3H4O, is the simplest unsaturated aldehyde (CH2=CHCHO). The primary characteristic of acrolein is its high reactivity due to conjugation of the carbonyl group with a vinyl group. More than 80% of the refined acrolein that is produced today goes into the synthesis of methionine. Much larger quantities of crude acrolein are produced as an intermediate in the production of acrylic acid. More than 85% of the acrylic acid produced worldwide is by the captive oxidation of acrolein. 

Silyl-l,3-dienes undergo anodic methoxylation in methanol to give 1,4-addition products with an allylsilane structure as intermediates. Therefore, they are further oxidized to give l,l,4-trimethoxy-2-butene derivatives as the final products. The products are easily hydrolyzed to provide the corresponding y-methoxy-a, /t-unsaUirated aldehydes. Since 1-trimethylsilyl-l,3-dienes are readily prepared by the reaction of the anion of l,3-bis(trimethylsilyl)propene with aldehydes or ketones, l,3-bis(trhnethylsilyl)propene offers a, /i-formylvinyl anion equivalent for the reaction with carbonyl compounds (equation 15)16. 

More than 300 compounds had been identified in cocoa volatiles, 10% of which were carbonyl compounds (59,60). Acetaldehyde, 2-methylpropanal, 3-methylbutanal, 2-methylbutanal, phenylacetaldhyde and propanal were products of Strecker degradation of alanine, valine, leucine, isoleucine, phenyl-acetaldehyde, and a-aminobutyric acid, respectively. Eckey (61) reported that raw cocoa beans contain about 50-55% fats, which consisted of palmitic (26.2%), stearic (34.4%), oleic (37.3%), and linoleic (2.1%) acids. During roasting cocoa beans these acids were oxidized and the following carbonyl compounds might be produced - oleic 2-propenal, butanal, valeraldehyde, hexanal, heptanal, octanal, nonanal, decanal, and 2-alkenals of Cg to C-q. Linoleic ethanal, propanal, pentanal, hexanal, 2-alkenals of to C q, 2,4-alkadienals of Cg to C-q, methyl ethyl ketone and hexen-1,6-dial. Carbonyl compounds play a major role in the formation of cocoa flavor components. 

Using ammonium cerium(IV) nitrate (CAN) as the oxidant for the azide anion, the azido radicals are trapped by alkenes, to form, ultimately, /i-azido nitrates84 cerium azide species may be considered as intermediates. Alkenes conjugated with carbonyl groups are recovered intact. The stereochemistry of the adducts from acenaphthylene and indene was trans, as shown by H-NMR studies (/AX < 2 Hz for the acenaphthylene adduct), but with (-Eyi-phenyl-l-propene both syn and anti additions were formed. 

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